The present invention relates to safety valves and, more particularly, to improvements in shut-off valves responsive to a rate of flow in excess of a predetermined value.
Valves are interposed in supply lines for liquid or gaseous fuels, and the like, to act as safety devices shutting off the flow when an unsafe condition exists. For example, if the volumetric flow rate of the gas exceeds a certain magnitude it is desirable to have some means of automatically shutting off the flow until the condition which caused the excess flow has been corrected. Since the failure to shut off flow under such conditions may result in loss of lives or property, it is imperative that the safety valve close reliably at the desired flow rate.
In utility gas service lines, it is desirable to install a safety shut-off valve relatively near the gas main, at least somewhat remote from the point of actual usage of the gas. In this way, the valve will not be damaged or fail to operate because of structural damage to the building where the gas is used, and may be installed below ground level to prevent malfunction due to tampering or other misuse. However, it is inconvenient or impossible to reset such valves because of their inaccessible location. Accordingly, it is commonly necessary to replace the safety shut-off valve with a new valve once it has been closed.
It is an object of the present invention to provide a novel and improved automatic shut-off valve operable in response either to excess flow of gas through the valve, or to the presence of other unsafe conditions, such as excessive temperatures.
Another object is to provide a basic valve design which may be tailored, by proper selection of the size, weight and other physical features of certain elements, to close in response to the flow rate through the valve exceeding any desired value.
A further object is to provide a safety shut-off valve having a single movable element which will operate repeatedly to close at a predetermined flow rate, within very close tolerances, when the pressure of the gas flowing through the valve is relatively low.
Still another object is to provide a safety shut-off valve movable to, and retained in, a closed position until reset by external means wherein the valve may be installed underground, or in an otherwise inaccessible position and reset from a remote location.
A still further object is to provide a method of operating a safety shut-off valve which includes resetting to the open position from a remote location in a simple and rapid manner.
Other objects will in part be obvious and will in part appear hereinafter.